I think it is one thing to potentially threaten the German transport and another actually going after it (at least with Russian FTRs). Personally I would never take the a risk like that. Those Russian FTRs are nearly impossible to replace and you need every bit of offensive trading power when the Ukr/ENO/Nov/Kaz battles present themselves. I suggest leaving the clearing of the German navy up to the USA or UK.
I never said it was a good idea, all I said was that it is a possibility.